This paper defines a measure of examinees' abilities using additivity, the fundamental proper... more This paper defines a measure of examinees' abilities using additivity, the fundamental property of a measure, based on the partially-credited item responses. The fundamental properties of this newly-defined ability measure are demonstrated using mathematical proofs. This paper also shows that interactive ability and conditional ability are measurable with additivity. Finally, the paper looks at the ability measures associated with subscales and their decompositions.
ABSTRACT Given a system of multiple random variables, a new measure called the L-multivariate ass... more ABSTRACT Given a system of multiple random variables, a new measure called the L-multivariate association coefficient is defined using (conditional) entropy. Unlike traditional correlation measures, the L-multivariate association coefficient measures the multiassociations or multirelations among the multiple variables in the given system; that is, the L-multivariate association coefficient measures the degree of the association for the given system. The L-multivariate association coefficient for the system of two random variables is also called the L-bivariate association coefficient. The association measured by the L-multivariate association coefficient is a general type of association, not any specific type of a linear or nonlinear association. Unlike the K-dependence coefficient, which is an asymmetrical measure, the L-multivariate association coefficient is a symmetrical measure. A direct application of the L-multivariate association coefficient is in variables selection or variables reduction. This paper also explores the relationship between the L-multivariate association coefficient and the K-dependence coefficient.
ABSTRACT In multivariate statistics, the linear relationship among random variables has been full... more ABSTRACT In multivariate statistics, the linear relationship among random variables has been fully explored in the past. This paper looks into the dependence of one group of random variables on another group of random variables using (conditional) entropy. A new measure, called the K-dependence coefficient or dependence coefficient, is defined using (conditional) entropy. This paper shows that the K-dependence coefficient is a measure of the degree of dependence of one group of random variables on another group of random variables. The dependence measured by the K-dependence coefficient includes both linear and nonlinear dependencies between two groups of random variables. Therefore, the K-dependence coefficient measures the total degree of dependence and not just the linear component of the dependence between the two groups of random variables. Furthermore, the concept of the K-dependence coefficient is extended by defining the partial K-dependence coefficient and the semipartial K-dependence coefficient. Properties of partial and semipartial K-dependence coefficients are also explored.
Chlamydial infection is a common bacterial sexually transmitted infection worldwide, caused by C.... more Chlamydial infection is a common bacterial sexually transmitted infection worldwide, caused by C. trachomatis. The screening for C. trachomatis has been proven to be successful. However, such success is not fully realized through tailoring the recommended screening strategies for different age groups. This is partly due to the knowledge gap in understanding how the infection is correlated with age. In this paper, we estimate age-dependent risks of acquiring C. trachomatis by adolescent women via unprotected heterosexual acts. We develop a time-varying Markov state-transition model and compute the incidences of chlamydial infection at discrete age points by simulating the state-transition model with candidate per-encounter acquisition risks and sampled numbers of unit-time unprotected coital events at different age points. We solve an optimization problem to identify the age-dependent estimates that offer the closest matches to the observed infection incidences. We also investigate t...
Organ transplantation and allocation has been a contentious issue in the U.S. for decades. The sc... more Organ transplantation and allocation has been a contentious issue in the U.S. for decades. The scarcity of donors highlights the need for improving the efficiency of the current policy. While the system is too complex for analytical modeling, agent-based modeling and simulation (ABMS), provides a promising approach to evaluate the allocation policy alternatives, since ABMS can model interactions of autonomous individuals in a network. In this paper, we develop an ABMS model in which organ procurement organizations (OPOs) and recipient candidates are modeled as agents. We model the multi-criteria decision making process for organ offering, in which we prioritize patients in the organ matching process in terms of mortality risk and geographic preference. We take liver transplantation and allocation as our case study for detailed policy modeling, input analysis, and output analysis. For future work, we plan to 1) incorporate more system heterogeneity, 2) develop a simulation optimizati...
Since the National Organ Transplant Act of 1984, the number of people receiving organs each year ... more Since the National Organ Transplant Act of 1984, the number of people receiving organs each year has increased [1]. Unfortunately, the number of donations has not kept up with the number of patients needing them, resulting in a severe shortage of organs [1]. This requires that we allocate organs as efficiently as possible. Currently in the U.S., organs are allocated at a local, regional, and national level in that order depending on patient-organ matches. In this paper, we consider the effect of region design on total intra-regional liver transplants and formulate it as a set partitioning problem.
We introduce the two-stage stochastic maximum-weight matching problem and demonstrate that this p... more We introduce the two-stage stochastic maximum-weight matching problem and demonstrate that this problem is NP-complete. We give a factor 1 2 approximation algorithm and prove its correctness. We also provide a tight example to show the bound given by the algorithm is exactly 1 2. Computational results on some two-stage stochastic bipartite matching instances indicate that the performance of the approximation algorithm appears to be substantially better than its worst-case performance. 2004 Elsevier B.V. All rights reserved.
Liver allocation policy uses the Model for End-Stage Liver Disease (MELD) for patients with chron... more Liver allocation policy uses the Model for End-Stage Liver Disease (MELD) for patients with chronic liver disease to stratify potential recipients according to the risk of waitlist death. The MELD is a Cox proportional hazardous model that is composed of three statistically significant mortality predictors. It has been shown to be a good indicator of mortality risk at a single point in a patient's course. However, there is a need for accurately predicting the progression of End-Stage Liver Disease (ESLD). Previous studies either did not consider a heterogeneous patient population awaiting liver transplantation or did not address changes in mortality risk over time. In a retrospective cohort study, we consider adult waitlist ESLD patients with multiple MELD score readings. We classify these patients via classification tree analysis. We identify a regression model for each patient class and then estimate the model parameters via traditional nonlinear regression and local regressio...
International Series in Operations Research & Management Science, 2011
Long-term care (LTC) provides medical and non-medical services to people with chronic disease or ... more Long-term care (LTC) provides medical and non-medical services to people with chronic disease or disability, many of whom are older adults eligible for receiving care through public funding sources. Annual spending on LTC in the United States exceeds $200 ...
We develop a computational modeling framework to study information processing in the auditory pat... more We develop a computational modeling framework to study information processing in the auditory pathway. Complex sounds consisting of a series of frequency modulated sweeps were used as test stimuli for our system. Frequency modu lation is an important factor in sound recognition and speech perception. Human behavioral data demonstrated that perception of the direction modulation (UP or DOWN) could be easily controlled in the stimuli by manipulating a single parameter. In order to analyze the represent ations to these stimuli in the peripheral auditory system, a two-stage process was employed. First, the stimuli were decomposed by a well-accepted model of the auditory nerve to produc e simulated auditory nerve outputs. Next, a neural network was developed to classify whether a given stimulus was going UP or DOWN. These data were compared to human behavioral data and neural activity in the rat auditory cortex. Outputs from the neural network model demonstrated that neurons could classi...
Purpose: Current guidelines on colorectal cancer (CRC) screening do not consider gender nor do th... more Purpose: Current guidelines on colorectal cancer (CRC) screening do not consider gender nor do they differ by age. Recent evidence, though, has shown that polyps form earlier and progress faster in men than women. Economic models for tailoring the guidelines need efficient and accurate quantification of model parameters, especially those governing the incidence and growth of adenomas for different age-gender groups. However, this model calibration is challenging given the large numbers of model parameters and outcomes. The purpose of our study is to generate insights into calibration of discrete-event simulations for CRC screening cost-effectiveness analyses. Methods: We developed a progressive fitting procedure to calibrate a discrete-event simulation model, which extended the 2007 Vanderbilt-NCSU CRC (VNCS) model by replacing each probability distribution governing adenoma state dwelling with a set of age-gender-specific distributions and synthesizing the probability distribution ...
In eukaryotic cells, secretory proteins and glycoproteins migrate from the rough endoplasmic reti... more In eukaryotic cells, secretory proteins and glycoproteins migrate from the rough endoplasmic reticulum, their site of synthesis, through Golgi vesicles before being released from the cell. Cellular and viral integral plasma membrane glycoproteins are co-translationally inserted into the rough endoplasmic reticulum membrane and follow a similar pathway to the cell surface. Previous studies using endoglycosidase H (Endo H) suggested that in rat hepatoma cells the vesicular stomatitis virus (VSV) G protein, albumin and transferrin migrate from the rough endoplasmic reticulum to the Golgi apparatus at different rates. Here we show directly that in human hepatoma HepG2 cells, five secreted proteins mature from the rough endoplasmic reticulum to Golgi vesicles at characteristic rates which differ at least threefold. The results are incompatible with bulk-phase movement of the luminal contents of the endoplasmic reticulum, and suggest that there is a membrane-bound receptor that selectivel...
Population health management is becoming increasingly important to organizations managing and pro... more Population health management is becoming increasingly important to organizations managing and providing primary care services given ongoing changes in health care delivery and payment systems. The objective of this study is to show how systems science methodologies could be incorporated into population health management to compare different interventions and improve health outcomes. The New York Academy of Medicine Cardiovascular Health Simulation model (an agent-based model) and data from the Behavioral Risk Factor Surveillance System were used to evaluate a lifestyle program that could be implemented in primary care practice settings. The program targeted Medicare-age adults and focused on improving diet and exercise and reducing weight. The simulation results suggest that there would be significant reductions projected in the proportion of the Medicare-age population with diabetes after the implementation of the proposed lifestyle program for a relatively long term (3 and 5 years...
Objectives. We assessed how systems science methodologies might be used to bridge resource gaps a... more Objectives. We assessed how systems science methodologies might be used to bridge resource gaps at local health departments (LHDs) so that they might better implement evidence-based decision-making (EBDM) to address population health challenges. Methods. We used the New York Academy of Medicine Cardiovascular Health Simulation Model to evaluate the results of a hypothetical program that would reduce the proportion of people smoking, eating fewer than 5 fruits and vegetables per day, being physically active less than 150 minutes per week, and who had a body mass index (BMI) of 25 kg/m(2) or greater. We used survey data from the Behavioral Risk Factor Surveillance System to evaluate health outcomes and validate simulation results. Results. Smoking rates and the proportion of the population with a BMI of 25 kg/m(2) or greater would have decreased significantly with implementation of the hypothetical program (P < .001). Two areas would have experienced a statistically significant red...
2011 IEEE International Conference on Automation Science and Engineering, 2011
ABSTRACT Chlamydia trachomatis infection, a major sexually transmitted disease, affects millions ... more ABSTRACT Chlamydia trachomatis infection, a major sexually transmitted disease, affects millions of people worldwide. A key public health challenge in managing such a transmitted disease is identifying infected but asymptomatic individuals so that they can be treated with antibiotics. Effectively resolving such a challenge will benefit both treated individuals (by improving quality of life) and the entire population (through reduced transmission). We adapt a well-established SEIRS (susceptible-exposed-infected-recovered-susceptible) model to evaluate the cost and effectiveness of different coverage levels of screening. To find the optimal screening rate, we formulate the question as a parameter optimization problem of ordinary differential equations and then apply a line search method which exhibits fast convergence. The numerical results as well as sensitivity analysis are presented in the paper.
This paper defines a measure of examinees' abilities using additivity, the fundamental proper... more This paper defines a measure of examinees' abilities using additivity, the fundamental property of a measure, based on the partially-credited item responses. The fundamental properties of this newly-defined ability measure are demonstrated using mathematical proofs. This paper also shows that interactive ability and conditional ability are measurable with additivity. Finally, the paper looks at the ability measures associated with subscales and their decompositions.
ABSTRACT Given a system of multiple random variables, a new measure called the L-multivariate ass... more ABSTRACT Given a system of multiple random variables, a new measure called the L-multivariate association coefficient is defined using (conditional) entropy. Unlike traditional correlation measures, the L-multivariate association coefficient measures the multiassociations or multirelations among the multiple variables in the given system; that is, the L-multivariate association coefficient measures the degree of the association for the given system. The L-multivariate association coefficient for the system of two random variables is also called the L-bivariate association coefficient. The association measured by the L-multivariate association coefficient is a general type of association, not any specific type of a linear or nonlinear association. Unlike the K-dependence coefficient, which is an asymmetrical measure, the L-multivariate association coefficient is a symmetrical measure. A direct application of the L-multivariate association coefficient is in variables selection or variables reduction. This paper also explores the relationship between the L-multivariate association coefficient and the K-dependence coefficient.
ABSTRACT In multivariate statistics, the linear relationship among random variables has been full... more ABSTRACT In multivariate statistics, the linear relationship among random variables has been fully explored in the past. This paper looks into the dependence of one group of random variables on another group of random variables using (conditional) entropy. A new measure, called the K-dependence coefficient or dependence coefficient, is defined using (conditional) entropy. This paper shows that the K-dependence coefficient is a measure of the degree of dependence of one group of random variables on another group of random variables. The dependence measured by the K-dependence coefficient includes both linear and nonlinear dependencies between two groups of random variables. Therefore, the K-dependence coefficient measures the total degree of dependence and not just the linear component of the dependence between the two groups of random variables. Furthermore, the concept of the K-dependence coefficient is extended by defining the partial K-dependence coefficient and the semipartial K-dependence coefficient. Properties of partial and semipartial K-dependence coefficients are also explored.
Chlamydial infection is a common bacterial sexually transmitted infection worldwide, caused by C.... more Chlamydial infection is a common bacterial sexually transmitted infection worldwide, caused by C. trachomatis. The screening for C. trachomatis has been proven to be successful. However, such success is not fully realized through tailoring the recommended screening strategies for different age groups. This is partly due to the knowledge gap in understanding how the infection is correlated with age. In this paper, we estimate age-dependent risks of acquiring C. trachomatis by adolescent women via unprotected heterosexual acts. We develop a time-varying Markov state-transition model and compute the incidences of chlamydial infection at discrete age points by simulating the state-transition model with candidate per-encounter acquisition risks and sampled numbers of unit-time unprotected coital events at different age points. We solve an optimization problem to identify the age-dependent estimates that offer the closest matches to the observed infection incidences. We also investigate t...
Organ transplantation and allocation has been a contentious issue in the U.S. for decades. The sc... more Organ transplantation and allocation has been a contentious issue in the U.S. for decades. The scarcity of donors highlights the need for improving the efficiency of the current policy. While the system is too complex for analytical modeling, agent-based modeling and simulation (ABMS), provides a promising approach to evaluate the allocation policy alternatives, since ABMS can model interactions of autonomous individuals in a network. In this paper, we develop an ABMS model in which organ procurement organizations (OPOs) and recipient candidates are modeled as agents. We model the multi-criteria decision making process for organ offering, in which we prioritize patients in the organ matching process in terms of mortality risk and geographic preference. We take liver transplantation and allocation as our case study for detailed policy modeling, input analysis, and output analysis. For future work, we plan to 1) incorporate more system heterogeneity, 2) develop a simulation optimizati...
Since the National Organ Transplant Act of 1984, the number of people receiving organs each year ... more Since the National Organ Transplant Act of 1984, the number of people receiving organs each year has increased [1]. Unfortunately, the number of donations has not kept up with the number of patients needing them, resulting in a severe shortage of organs [1]. This requires that we allocate organs as efficiently as possible. Currently in the U.S., organs are allocated at a local, regional, and national level in that order depending on patient-organ matches. In this paper, we consider the effect of region design on total intra-regional liver transplants and formulate it as a set partitioning problem.
We introduce the two-stage stochastic maximum-weight matching problem and demonstrate that this p... more We introduce the two-stage stochastic maximum-weight matching problem and demonstrate that this problem is NP-complete. We give a factor 1 2 approximation algorithm and prove its correctness. We also provide a tight example to show the bound given by the algorithm is exactly 1 2. Computational results on some two-stage stochastic bipartite matching instances indicate that the performance of the approximation algorithm appears to be substantially better than its worst-case performance. 2004 Elsevier B.V. All rights reserved.
Liver allocation policy uses the Model for End-Stage Liver Disease (MELD) for patients with chron... more Liver allocation policy uses the Model for End-Stage Liver Disease (MELD) for patients with chronic liver disease to stratify potential recipients according to the risk of waitlist death. The MELD is a Cox proportional hazardous model that is composed of three statistically significant mortality predictors. It has been shown to be a good indicator of mortality risk at a single point in a patient's course. However, there is a need for accurately predicting the progression of End-Stage Liver Disease (ESLD). Previous studies either did not consider a heterogeneous patient population awaiting liver transplantation or did not address changes in mortality risk over time. In a retrospective cohort study, we consider adult waitlist ESLD patients with multiple MELD score readings. We classify these patients via classification tree analysis. We identify a regression model for each patient class and then estimate the model parameters via traditional nonlinear regression and local regressio...
International Series in Operations Research & Management Science, 2011
Long-term care (LTC) provides medical and non-medical services to people with chronic disease or ... more Long-term care (LTC) provides medical and non-medical services to people with chronic disease or disability, many of whom are older adults eligible for receiving care through public funding sources. Annual spending on LTC in the United States exceeds $200 ...
We develop a computational modeling framework to study information processing in the auditory pat... more We develop a computational modeling framework to study information processing in the auditory pathway. Complex sounds consisting of a series of frequency modulated sweeps were used as test stimuli for our system. Frequency modu lation is an important factor in sound recognition and speech perception. Human behavioral data demonstrated that perception of the direction modulation (UP or DOWN) could be easily controlled in the stimuli by manipulating a single parameter. In order to analyze the represent ations to these stimuli in the peripheral auditory system, a two-stage process was employed. First, the stimuli were decomposed by a well-accepted model of the auditory nerve to produc e simulated auditory nerve outputs. Next, a neural network was developed to classify whether a given stimulus was going UP or DOWN. These data were compared to human behavioral data and neural activity in the rat auditory cortex. Outputs from the neural network model demonstrated that neurons could classi...
Purpose: Current guidelines on colorectal cancer (CRC) screening do not consider gender nor do th... more Purpose: Current guidelines on colorectal cancer (CRC) screening do not consider gender nor do they differ by age. Recent evidence, though, has shown that polyps form earlier and progress faster in men than women. Economic models for tailoring the guidelines need efficient and accurate quantification of model parameters, especially those governing the incidence and growth of adenomas for different age-gender groups. However, this model calibration is challenging given the large numbers of model parameters and outcomes. The purpose of our study is to generate insights into calibration of discrete-event simulations for CRC screening cost-effectiveness analyses. Methods: We developed a progressive fitting procedure to calibrate a discrete-event simulation model, which extended the 2007 Vanderbilt-NCSU CRC (VNCS) model by replacing each probability distribution governing adenoma state dwelling with a set of age-gender-specific distributions and synthesizing the probability distribution ...
In eukaryotic cells, secretory proteins and glycoproteins migrate from the rough endoplasmic reti... more In eukaryotic cells, secretory proteins and glycoproteins migrate from the rough endoplasmic reticulum, their site of synthesis, through Golgi vesicles before being released from the cell. Cellular and viral integral plasma membrane glycoproteins are co-translationally inserted into the rough endoplasmic reticulum membrane and follow a similar pathway to the cell surface. Previous studies using endoglycosidase H (Endo H) suggested that in rat hepatoma cells the vesicular stomatitis virus (VSV) G protein, albumin and transferrin migrate from the rough endoplasmic reticulum to the Golgi apparatus at different rates. Here we show directly that in human hepatoma HepG2 cells, five secreted proteins mature from the rough endoplasmic reticulum to Golgi vesicles at characteristic rates which differ at least threefold. The results are incompatible with bulk-phase movement of the luminal contents of the endoplasmic reticulum, and suggest that there is a membrane-bound receptor that selectivel...
Population health management is becoming increasingly important to organizations managing and pro... more Population health management is becoming increasingly important to organizations managing and providing primary care services given ongoing changes in health care delivery and payment systems. The objective of this study is to show how systems science methodologies could be incorporated into population health management to compare different interventions and improve health outcomes. The New York Academy of Medicine Cardiovascular Health Simulation model (an agent-based model) and data from the Behavioral Risk Factor Surveillance System were used to evaluate a lifestyle program that could be implemented in primary care practice settings. The program targeted Medicare-age adults and focused on improving diet and exercise and reducing weight. The simulation results suggest that there would be significant reductions projected in the proportion of the Medicare-age population with diabetes after the implementation of the proposed lifestyle program for a relatively long term (3 and 5 years...
Objectives. We assessed how systems science methodologies might be used to bridge resource gaps a... more Objectives. We assessed how systems science methodologies might be used to bridge resource gaps at local health departments (LHDs) so that they might better implement evidence-based decision-making (EBDM) to address population health challenges. Methods. We used the New York Academy of Medicine Cardiovascular Health Simulation Model to evaluate the results of a hypothetical program that would reduce the proportion of people smoking, eating fewer than 5 fruits and vegetables per day, being physically active less than 150 minutes per week, and who had a body mass index (BMI) of 25 kg/m(2) or greater. We used survey data from the Behavioral Risk Factor Surveillance System to evaluate health outcomes and validate simulation results. Results. Smoking rates and the proportion of the population with a BMI of 25 kg/m(2) or greater would have decreased significantly with implementation of the hypothetical program (P < .001). Two areas would have experienced a statistically significant red...
2011 IEEE International Conference on Automation Science and Engineering, 2011
ABSTRACT Chlamydia trachomatis infection, a major sexually transmitted disease, affects millions ... more ABSTRACT Chlamydia trachomatis infection, a major sexually transmitted disease, affects millions of people worldwide. A key public health challenge in managing such a transmitted disease is identifying infected but asymptomatic individuals so that they can be treated with antibiotics. Effectively resolving such a challenge will benefit both treated individuals (by improving quality of life) and the entire population (through reduced transmission). We adapt a well-established SEIRS (susceptible-exposed-infected-recovered-susceptible) model to evaluate the cost and effectiveness of different coverage levels of screening. To find the optimal screening rate, we formulate the question as a parameter optimization problem of ordinary differential equations and then apply a line search method which exhibits fast convergence. The numerical results as well as sensitivity analysis are presented in the paper.
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